Refrigerating apparatus



July 11, 1944- A A. `A. MCCORMACK 2,353,347

` REFRIGERATING APPARATUS Filed sept. 13, 1 941 Patented July `l l, 1944 UNITED ASTATES PATENT OFFICE" Alex A. McCormack, Dayton, Ohio,

General Motors Corporation, .corporation of Delaware sssignor to 1 Dayton, Ohio, a

Application septemberis; 1941, semi No. 410352 '(01. cs2-s) 7Claims.

This invention relates to refrigerating apparatus and more particularly to apparatus for controlling the operation oi' a refrigerating system.

It is an object of this invention to provide means whereby a lgiven size motor-compressor unit may be used on widely varying refrigerationloads without sacrificing motor eillciency.

Another object of this invention is to provide means which makes it possible to operate a refrig'erant compressor in a lower'pressure range so as to avoid excessive heating of the motorcompressor unit. e

More specifically. it is an object of this invention to provide means for reducing the load on a`y compressor motor by restricting the flow ot refrigerant tothe compressor when the head pressure becomes excessive.

, Another object is to provide a simpleand inexpensive control device which may .be added to existing refrigeration systems.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred form of the present invention is clearly shown.

In the drawing: Y

.lllg l is a view partly diagrammatic and partly in section showing my invention applied to a conventional refrigerating system, and

' Fig. 2 is an enlarged sectional view showing `the refrigerant flow control device in that position which it occupies when the head pressure is excessively high.

Since the load on a refrigerating system fre-` quently varies from day to day due to changes in the temperature of the condenser cooling medium and the like, it is necessary that the motorcompressor unit have a capacity considerably in excess of the average requirements. Since it is not practical from a standpoint of emciency in operation to Provide an oversized motor capable of operating the compressor at the highest pressures encountered. it is the purpose of my invention to provide a control means for preventing overloading of the motor at these high'pres-4 sures.- It is common practice to provide means for controlling the ,back pressure in a refrigerating system but all such means now in use either reduce the emcieney of the system or otherwise interfere with the proper operation of the'sys- It is also common practice to provide protective devices suchas high pressure cut outs for stopping the compressoror for otherwise"render ing the compressor inetective when the load on the compressor becomes excessive. In many refrigeration installations, however, a high head pressure does not mean that operation of the compressor is nolonger required since the high head pressure may be due to insuillcient con-- denser capacity. Consequently, it is desirable to continue compressing refrigerant at times when both the back pressure and the head pressure exl lceeclA the pressures for which the compressor is designed to operate. In order to continue the operation of the compressor under such high pressure conditions, it is necessaryto reduce the load on the compressor. The method and apparatus vdescribed herein makes it possible to continue the operation of the compressor at a reduced capacity when the pressure in the refrigerating system exceeds that for which. the

compressor is designed to normally operate.

Referring to Fig. 1, in which I have shown my invention applied to a conventional refrigerating f system, reference numeral IB designates a conis supplied toA the condenser 24 through the vap I por line 26Y leading from the casing I2 to the condenser' 2E The condensed refrigerant collects in the receiver 28 from which it is supplied to the evaporator I0. 'I'he flow of refrigerant from the receiver 2l to the evaporator 30 is controlled by a conventional thermostatic expansion valve 22. The thermostatic expansion valve l2 includes the usual thermostatic bulb 34 arranged in thermal exchange relationship with the last pass of the evaporator in accordance with wellr known practice. The refrigerant` vaporized in the evaporator JI is returned to the compressor through the suction line 36.

In order to control the now of refrigerant from the evaporator to the compressor, I have provided a control unit designated in general by the vreference numeral Il. The control unit 28 comprises a gas passage 2l and a. valve element 4I4 carried by a plungerelement I2. A spring M v biases the valve element II into the fully open pomtion in which it is shown in Fig. l. In this position of the valve. the vapor leaving the evaporator Il is to -ilow without restriction ,through the passage 2l to the compressor inlet the vapor line so as to prevent the flow of refrigerant or lubricant from the compressor into passage 39 and the vapor line 36.

The control unit 38 includes a passage 50 which communicates with the motor-compressor casing i2 at a point below the level vof the lubricant t4. The lubricant I4 is subjected to a pressure corresponding to the high side pressure and is used for controlling the operation of the valve 40. The passage 5|) supplies lubricant to the lower end of the valve plunger 42, with the result that as the pressure on the lubricant becomes excessively high the plunger 42 together with its associated valve element 40 is moved upwardly so as to restrict the return of refrigerant vaporto the compressor. Inasmuch as it is not the purpose of the valve 40 to completely cut off the flow of refrigerant to the compressor, a small amount of clearance 52 is provided between the valve element 40 and the outer walls of the refrigerant passage 39.

The lubricant which contacts the lower end of the plunger 42 not only serves to lubricate the plunger but also serves as a liquid seal preventing the leakage of high pressure gas past the plunger into the low side of the system. y

By adding asimple control of thetype disclosed herein to an ordinary refrgeratinglsystem, the same: motor and condenser is capable of operating at higher condensing temperatures. Thus, by using my improved control, a conventional 've horse power unit may be used inA a system which would otherwise require a six or seven horse power unit since the compressor will continue to operate at the higher refrigerant pressures which occur only during peak loads. As pointed out hereinabove, the valve 40 will restrict the flow of refrigerant to the compressor at the higher head pressures but the compressor will still operatel to compress refrigerant vapor at a high rate. Since it is not necessary to provide an oversized motor to provide refrigeration during peak loads, it is apparent that a five horse power ref rigerating system constructed in accordance with my invention operates more eiciently at lower loads than a system using a larger motor.

Since the peak load for which a refrigerazting system must be designed may never be reached,

it is apparent that a system designed according to my invention will operate with the valve 40 fully open in many installations -for a maior portion of the time.

`While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all com ing within the scope of the claims which follow.

What is claimed is as follows:

1. In combination; an evaporator, a condenser; a compressor including a lubricant supply casing into which said compressor discharges; refrigerant flow connections between said evaporator, condenser and compressor including a suction line in a predetermined position of said plunger, and spring means for opposing the force exerted by the lubricant against said plunger.

2. Ina refrigerating system, a compressor, an evaporator, a condenser, refrigerant ilow connections between salid compressor, condenser and evaporator, refrigerant flow control means between said evaporator and condenser separating said system into a high pressure portion and a low pressure portion, means providing a passage `from the high pressure portion vto the low pressure portion, a piston in said passage having one end subjected to the high pressure and the other end subjected to the low pressure, means operated by said plunger restricting the flow of refrigerant to said compressor, and means for supplying lubricant to the high pressure end of said passage so as to lubricate said piston and provide a liquid seal between said piston and the walls of said passage. l

3. In combination; a compressor; a lubricant supply casing enclosing said compressor; means whereby said compressor discharges into said casing; a suction line leading to the inlet of said compressor; and an adapter provided in said suction line including vmeans for restricting the flow in said suction line; said adapter having a passage communicating with the interior of said lubricant supply casing at a point below the lubricant level therein and also communicating with the suction line, a plunger disposed in said passage preventing the flow of lubricant through said passage and having means for restricting the flow of refrigerant in said suction line in a predetermined position of said plunger, and spring .means for opposing the force exerted by the lu- Y bricant against said plunger.`

line between said evaporator and the inlet of said compressor; and means `for restricting the flow of refrigerant in said suction line; said means comprising a passage leading from a point below the lubricant level in said lubricant supply casing to the suction line. a plunger disposed in.

4. In a compressor including a lubricant supply casing into which said compressor discharges; a suction line leading to the inlet of said compressor; and means for restricting the flow in said suction line; said vmeans comprising a passage leading from a point below the lubricant level in said lubricant supplycasing to the suction line, a plunger disposed in said passage preventing the ilow of lubricant through said passage and having means for restricting the ow of refrigerant in said suction line in a predetermined' position of said plunger, and spring means for opposing the force exerted by the lubricant against said plunger.

5. In a compressor having a low pressure inlet chamber and a high pressure outlet chamber, means providing a passage from the high pressure chamber to the low pressure chamber, a. piston in said passage having one end subjected to the high pressure and the other end subjected to Vthe low pressure, means operated by said plunger f restricting the now to the inlet of said compressor, and means for supplying lubricant to said passage so as to lubricate said piston and provide a` liquid seal between said piston and the walls ofsaid passage.

6. In combination; an evaporator; a condenser; a compressor including a lubricant supply casing into which said compressor discharges; refrigerant now connections, between said evaporator, condenser and compressor including a suction line between said evaporator and the inlet of said compressor; and an adapter mounted in said suction line including means for restricting the flow of refrigerant in said suction line; said Aadapter comprising a passage leading from a line; said means comprising a passage leading from a point below the lubricant level in said lubricant supply casing to the suction line, a plunger disposed in said passage preventing the iiow of lubricant through said passage and having means for restricting the iiow of refrigerant in said suction line in a predetermined position of said plungenand spring means for opposing the force exerted by the lubricant against said plunger, said passage and said plunger being provided in an adapter mounted externally of said casing.

ALEX A. MCCORMACK. 

